5 Weird Workout Side Effects

Clearly, hoisting 50-pound dumbbells over your face is not the time for a dizzy spell. And like the shakes, dizziness may be due to several different factors, says Veselik. Reasons behind it vary according the specifics. Vertigo can occur when you're leaning back and the room appears to spin, or significant dehydration can lead to a state called hypovolemia, or low blood volume, which may produce dizziness, says Higgins.

How to reduce your risk: Immediately stop working out and drink some water. Vertigo is likely an inner ear problem, says Veselik, and requires working with a physical therapist trained in vestibular therapy. If you're a normal healthy guy and you feel unusually dizzy for a few minutes or longer, call a doctor. It may be a sign of a heart arrhythmia or other heart problem.

Contrary to what you see on The Biggest Loser, nausea during a workout is not normal, and it may be triggered by a number of different things. Eating the wrong food at the wrong time or pushing yourself too hard can all cause queasiness and even vomiting. "If you're working out to that extent ,back off and gradually acclimate to that intensity over time," says Veselik. Nausea can also occur from taking vitamins on an empty stomach, says Higgins. "It's more common with supplements high in iron, multivitamins with herbal additives, and those containing lots of fillers and binders." Taking other medications at the same time as your vitamins, such as caffeine or birth control pills, may make it worse.

How to reduce your risk: Take vitamins with food, preferably at breakfast or lunch. And if you repeatedly suffer from nausea, you might want to void eating solid food three hours prior to a workout. For a more easily digestible, quick-energy alternative, try a liquid meal replacement that includes carb and protein about 30 to 60 minutes before you exercise.